In a smart grid technology where an electrical power and communication/information technology converges, a problem of unbalance of supply and demand due to discordance between electrical power production and demand can be solved by using a method of demand/response.
A technology for demand/response consists of two types. The first type is a method by policy and the second type is a method for controlling demand of electrical power by real time price fluctuation process.
The first type is a method where a supply of electrical power is stopped according to importance of an electrical power consumer when the supply of the electrical power is not sufficient. The second type is a method for leading reduction of electrical power consumption according to ability of a consumer by setting a supply price of electrical power according to demand of electrical power in order to solve the unbalance of supply and demand.
However, in such smart grid environment of the method of demand/response, although an electrical power producer which supplies power to a specific user can supply sufficient power to the specific user, the specific user may instead have to put up with a problem of the electrical power supply shortage generated in other systems. In addition, a problem that a user has to accept a relative loss may be brought since the electrical power consumption generated by other factors is reflected in price.